development and validation of the visual functioning index

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Middle East African Journal of Ophthalmology, Volume 19, Number 3, July - September 2012

Original Article

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, 1King Fahd Hospital, Al Baha, Saudi Arabia

Corresponding Author: Dr. Ahmed Mousa, Lecturer, Department of Ophthalmology, King Abdul Aziz University Hospital, College ofMedicine, King Saud University, Riyadh 11411, P.O. Box: 245, Saudi Arabia. E-mail: [email protected]

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DOI:

10.4103/0974-9233.97932

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INTRODUCTION

Cataract is the major cause of low vision and blindness inthe Middle East (45.2%) and worldwide (50%).1,2 In theMiddle Eastern region, 31.4 million individuals aged 60 years orolder and 20.8 million below 60 years of age are visually disableddue to cataract.3 As the volume of cataract surgery increases due

to the aging population, there is a need to continually monitorand evaluate surgical outcomes and the impact on visual functionand quality of life. The Visual Functioning Index VF-14 wasdeveloped and validated by Steinberg and colleagues in theearly nineties.4 The rationale for developing this index was the

need for a tool that can accurately measure cataract surgeryoutcomes as visual acuity alone was considered as an insufficientmeasure.5,6 Since its introduction, the VF-14 has been widelyaccepted and utilized for various ocular diseases that can affect

vision including estimation of the need and urgency of cataractsurgery. The VF-14 has been used to evaluate and comparedifferent surgical procedures. This index has been used forglaucoma, retina, cornea, keratoplasty, macular degeneration,low vision, and prevention of blindness research.7-11

The VF-14 was originally developed in English for developedcountries, consequently, there was a debate regarding its

ABSTRACT

Purpose: To develop and validate an Arabic version of the Visual Functioning Index (VF-14)for patients with cataracts.Materials and Methods: The VF-14 was translated into Arabic by an epidemiologist and anophthalmologist, both uent in Arabic and English. The VF-14 was administered to patientsdiagnosed with cataract at two hospitals in Egypt and two hospitals in Saudi Arabia.Patients were also administered three other forms; the cataract symptoms score (CSS); globalmeasure of vision; and cataract medical form. Internal reliability and external validity weremeasured. Index sensitivity to visual acuity was detected and potential effective factors wereinvestigated. Correlation analyses were performed. A p value less than 0.05 was consideredstatistically signi cant.Results: The translated VF-14 was consistent and reliable ( = 0.763, p < 0.0001). It wasalso statistically signi cantly sensitive to vision ( p < 0.0001). The mean calculated index was62.18 19.34, and was highly correlated with; CSS and other scores ( p < 0.0001, all cases).Factors that may affect the index are; age, sex, vision, wearing glasses, type, position, andseverity of cataract.Conclusion: The Arabic VF 14 is a reliable and valid tool for evaluation of both visualfunctioning and quality of visual life among cataract patients. It is also sensitive to changes

in visual acuity, demographic, and clinical characteristics.

Key words: Cataract Outcome, Validation, Visual Function Index, Visual Function

Development and Validation of an Arabic Versionof the Visual Functioning Index VF-14 for CataractPatientsAhmed Mousa, Ali H. Al Ghamdi 1, Hatem Kalantan, Abdul R. Al Muammar


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Mousa,et al .: Development and Validation of an Arabic Visual Function Questionnaire

global validity. Therefore, various investigators have translated,modified and validated the VF-14 to suit different languagesand settings. The VF-14 has proved to be reliable, valid, andhighly consistent when used for different purposes, in differentlanguages and settings.

In 1999, Karin van Dijk and colleagues (1999) validated amodified version for African countries where a lot of researchto prevent blindness specifically from cataract takesplace.12 In the Middle East, Arabic is spoken in 22 Arabiccountries with a total population of 291 million inhabitants.

Additionally, the prevalence of blindness in this region is one ofthe highest.13 There is also a dramatic increase in ocular researchthat mandates the need to develop and validate a reliable Arabic

version of the VF-14. Therefore, we sought to translate, adapt,and validate an Arabic version of the VF-14 for subsequent usein ophthalmologic research.

MATERIALS AND METHODS

The current study was conducted in a cross sectional studydesign. The original VF-14 questionnaire was separatelytranslated into Arabic by two different ocular researchers(an epidemiologist from Egypt and an ophthalmologist fromSaudi Arabia who were fluent in both Arabic and English).Subsequently the two versions were matched and unified.The new Arabic questionnaire was translated back to Englishby a third researcher (ophthalmologist) and then matched tothe original version by an optometrist whose native language

was English. Minimal modifications were required by theresearch team to formulate a final version of the Arabic VF-14questionnaire to suit the Arabic culture.

Three other forms were administered in parallel with the VF-14 form including the Cataract Symptoms Score (CSS),Global Measure of Vision (including; Trouble and Satisfaction

with current vision forms), and a cataract medical form whichcollected information on patient demographics, visual acuity,and grade, type, and position of cataract. Cataract categorizationand grading were simplified and standardized using internationalguidelines.14-16 Meanwhile, patient visual acuity classificationfollowed the World Health Organization (WHO) standardizedguideline.17,18

Scoring and scaling systemEach of the VF-14 questions was given a score ranging from0 4 as follows; 4; no difficulty , 3; a little difficulty , 2; moderate

difficulty , 1; a great deal of difficulty and 0; Unable to do the activity while not applicable was left blank and excluded fromthe analysis. The scores were added for all questions and thetotal was divided by the total number of answered questions. Thetotal score was then multiplied by 4 to get the overall index foreach person which indicated the patients visual functioning scale

ranging from (0 100) where 0 meant unable to do all applicableactivities, and 100 means best possible visual functioning.Likewise, the global measure of vision index (trouble andsatisfaction with current vision) were scored in terms of troubleas; 0; None, 1; A little, 2; A moderate amount, 3; A great

deal and in terms of satisfaction as; 3; Very dissatisfied, 2; Moderately dissatisfied, 1; Satisfied, and 0; Very satisfied. TheCSS was calculated as; 3; Very bothered, 2; Somewhat bothered,1; A little bothered and 0; Not at all bothered. Calculations ofthe overall index were performed through summing the totalresults in a cataract symptoms index for each patient rangingfrom 0 ( no symptoms or not bothered by any of the symptoms) to 15(very bothered by all five symptoms).

Implementation of the indexThe integrated package of forms was administered to a totalof 1413 cataract patients from two hospitals in Egypt and twoothers in Saudi Arabia. Patients recruited for the study werescheduled for surgery within 3 months (maximum). Inclusioncriteria were; Arabic as a native language, age of 20 years or older,no prior ocular surgery, no combined procedures, in additionto absence of any ocular co-morbidities.

Statistical analysis and validationData management/verification processes were conducted andall ineligible data were removed due to; missing, incomplete,facing contradictions, and or inconsistencies. Validation processincluded three phases; (1) scoring and descriptive analysis, (2)internal consistency testing (reliability) using Cronbachs test,(3) testing validity by evaluating correlation between the VF-14score and; the logarithm of the minimum angle of resolution(LogMAR) visual acuity, CSS, Visual Trouble Score, and VisuaSatisfaction Score using Pearsons correlation coefficient. One

way analysis of variance (ANOVA) was performed to investigatthe sensitivity of the VF-14 to different levels of visual acuity

while multiple linear regression was conducted to investigatedifferent factors affecting the new index. A p value less than 0.05

was considered statistically significant. The unit of analysis wasthe person (not eye) where; visual acuity and the correspondinggroup of vision were calculated as an average of (0.25* the worseeye + 0.75* the best eye).

Ethics approval was obtained from the Institutional Researchand Ethics Board (IREB) of King Saud University (IREB-09-702) and the study conformed to the tenets of the Declarationof Helsinki.

RESULTS

The index was administered to patients booked for cataractsurgery from March 1st to September 30th 2010 who met theinclusion criteria. During data management, 33 cases wereexcluded leaving a total of 1380 patients. The study cohort was


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recruited from the following institutions; 324 (23.5%) patientsfrom King Abdul Aziz University Hospital, Riyadh; 186 (13.5%)patients from King Fahd Hospital, Baha; 522 (37.8%) patientsfrom Magrabi Eye Hospital, Cairo and; 348 (25.2%) patientsfrom Magrabi Eye Center, Tanta. The first two hospitals werebased in two different governorates in Saudi Arabia and the othertwo hospitals were based in two different governorates in Egypt.

The mean age (SD) was 63.41 11.19 years (range, 24 yearsto 80 years). There were 840 (60.9%) males and 540 (39.1%)females. The majority (840; 60.9%) of patients were undergoingsurgery on the left eye and 720 (52.2%) patients had visualacuity = 20/40 11 80.29 (6.57) (75.88 84.70)20/50 - 20/160 769 74.23 (12.10) (73.37 75.09)20/200 - 20/400 270 56.45 (13.09) (54.88 58.01)CF, HM, LP, NLP 330 38.19 (11.38) (36.96 39.42)Total 1380 62.18 (19.34) (61.16 63.20)

CF: Counting ngers, HM: Hand movement, LP: Light perception, NLP: No lightperception

Table 4: Matrix of Binary Differences between Groups (Post Hocanalysis)

Group I Group II MeanDifference

S. E. P value 95%Condence

IntervalNormal Low vision 6.06 3.68 0.351 (-3.39 15.52)

Severe lowvision

23.85 3.72


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Italian, Spanish, Turkish, Brazilian, Chinese, and several otherlanguages. The VF-14 index was found to have good validity aftertranslation and validation into different languages with minimaladaptation to each language. The rationale for this localizationis to adjust for the cultural and other community specificdifferences. Additionally, there were many attempts to developsimilar indices for different age groups.19,20 However, the VF-14showed convenient flexibility either to minimal modifications,reproducibility,21 or to shortening of its questions where itpersisted to be reliable and valid.22 Despite the availability ofsimilar indices such as the National Eye Institute NEI VFQ 25, orthe WHO VF 20, the VF-14 which was developed as cataractspecific was then widely utilized for evaluation of other ocularinterventions including long term follow up.23 Furthermore, the

VF-14 proved to be a reliable tool for decision making 24 andprioritization of waiting lists in cataract surgeries.

In an effort to cope with the tremendous increase in ocularresearch in many Arabic speaking countries, we translatedand minimally modified the VF-14 for use in Arabic speakingcountries and communities. The new index showed highlysignificant reliability and validity and was comparable to classicoutcome assessment indices including; LogMAR visual acuity,dissatisfaction, and trouble with vision indices (global measuresof vision). The CSS is widely accepted as a reliable, valid, and

very sensitive tool to assess cataract patients preoperatively. Itis internationally recognized as a highly correlated index to the

VF-14.25,26 Our results are consistent with this internationaltrend. Hence, using the Arabic version would enable internationalcomparisons in addition to standardization of quality eye care.The sensitivity of the Arabic VF-14 to change in vision issimilar to the findings of Steinberg and co-workers4 and thegeneral trend to other translation and validation studies.25,26 This provides additional evidence on the reliability and validityof the VF-14 as a tool for measuring visual functioning forcataract patients. Additional studies are required to assess the

effectiveness of the Arabic VF-14 in other ocular diseases andto use it as a tool for evaluation and comparison of differentprocedures.

CONCLUSION

The findings of this study indicate that the Arabic VF-14 is areliable and valid tool for evaluation of both visual functioningand quality of visual life among cataract patients preoperatively.The new Arabic tool can be affected by age, sex, spectacle wear,in addition to different levels of vision and the maturity, severity,type, and position of cataract. The Arabic VF-14 is highlyrecommended for evaluating visual function as an outcomeindicator of surgical intervention either in cataract or in otherocular diseases after pre-testing. It can also be used in decisionmaking process for surgical interventions and for prioritizationof surgical waiting lists.

REFERENCES

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Figure 1: Pattern of visual functioning index (VF 14) with different levels of visualacuity



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Cite this article as: Mousa A, Al Ghamdi AH, Kalantan H, Al Muammar AR.Development and validation of an Arabic version of the visual functioning indexVF-14 for cataract patients. Middle East Afr J Ophthalmol 2012;19:309-13.

Source of Support: Nil, Con ict of Interest: None declared.

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Diener-West M, et al . Reproducibility and responsiveness ofthe VF-14. An index of functional impairment in patients withcataracts. Arch Ophthalmol 1995;113:1508-13.

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26. Lee JE, Fos PJ, Sung JH, Amy BW, Zuniga MA, Lee WJ, et al .Relationship of cataract symptoms of preoperative patients andvision-related quality of life. Qual Life Res 2005;14:1845-53.


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development and validation of the visual functioning index

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